The invention is in the field of depositing thin films and, more particularly, relates to a method of depositing thin films by reactive sputtering followed by treatment with reactive ions as for example by a reactive ion beam, both performed in the same atmosphere comprising a mixture of reactive and inert gases.
There are many instances, such as in optical applications, in which it is desirable to deposit an oxide film or coating on a substrate. Various methods are known in the prior art for depositing such coatings.
One method known to the prior art is depositing an oxide coating on a substrate by RF sputtering, in which a frequency of the order of 13.56 MHz is applied between the xe2x80x9canodexe2x80x9d electrode and the target xe2x80x9ccathodexe2x80x9d in a highly oxidizing atmosphere.
Quasi Patent 4,693,805 discloses reactive sputtering in which positive DC pulses are applied between the anode and the target in the presence of oxygen. When the voltage difference between the anode and the target is zero, a negative DC voltage pulse is applied between the target and a secondary cathode to discharge oxide layers on the target and eliminate the problem of target arcing. The patentee indicates that low frequency power supplies may be used but always in an atmosphere having a sufficiently high oxygen content that only metal oxide is sputtered and no elemental metal.
One object of my invention is to provide a method of forming a thin oxide coating more rapidly than is possible in the prior art by sputtering both elemental metal and metal oxide.
Another object of my invention is to provide a method of sputtering a thin oxide coating on a substrate which allows close control of the coating applied.
A still further object of my invention is to provide a method of reactive sputtering at relatively low frequency.
Other and further objects of my invention will appear from the following description.